Current transformer with calibration information

ABSTRACT

A current transformer assembly includes a first current transformer, a plug, a first wire and a second wire between the plug and the first current transformer adapted to transmit a measurement of the first current transformer; and a memory chip adapted to store a first scale factor of the first current transformer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/873,132, filed Jul. 11, 2019, and entitled “CurrentTransformer Apparatus” (SAGE-0007-P01). The foregoing application isincorporated herein by reference in its entirety for all purposes.

FIELD OF INVENTION

The apparatus described herein generally relate to a current transformerfor attaching to and measuring electrical current through one or moreelectrical mains.

BACKGROUND

Reducing electricity or power usage provides the benefits, among others,of saving money by lowering payments to electric companies and alsoprotecting the environment by reducing the amount of resources needed togenerate the electricity. Electricity users, such as consumers,businesses, and other entities, may thus desire to reduce theirelectrical usage to achieve these benefits. Users may be able to moreeffectively reduce their electricity usage if they have informationabout electricity usage.

Power monitors for individual devices are available for measuring thepower usage of a single device. For example, a device can be pluggedinto a power monitor, and the monitor can in turn be plugged into a walloutlet. These power monitors can provide information about power usagefor the one device they are attached to, but it may not be practical tomonitor all or even many devices in a house or building with these powermonitors, because it would require a large number of devices that can beexpensive and also require significant manual effort to install.

Instead of a power monitor for a single device, a power monitor can beinstalled at an electrical panel to obtain information about electricityused by many devices simultaneously over one or more electrical mainseach providing, for example, 120 volts. The ability to monitor theelectricity passing through one or more electrical mains may be enhancedby a physical link to each main capable of sensing the electricitypassing through the main. However, various codes restrict the amount ofspace available to situate a device or devices to perform such sensing.

What is therefore needed is a device adapted to attach to or in closeproximity to an electrical main that is capable of sensing electricalcurrent through the mains that is compact and easily manipulated.

SUMMARY

In accordance with an exemplary and non-limiting embodiment, a currenttransformer may include a first housing having a first handle portionand a first distal portion; a second housing having a second handleportion and a second distal portion; a first core having a firstproximal core end and a first distal core end, the first core mounted inrotational contact within the first distal portion; and a second corehaving a second proximal core end and a second distal core end, thesecond core mounted in rotational contact within the second distalportion; wherein the first housing is rotationally coupled to the secondhousing about a fulcrum point and wherein, when the first housing andthe second housing are rotated into a closed position, the first core isadapted to rotate within the first distal portion and the second core isadapted to rotate within the second distal portion to enable contactbetween the first proximal core end and the second proximal core end andto enable contact between the first distal core end and the seconddistal core end. In embodiments, the pivot member may be attached to thefirst core and the first housing includes an indentation to receive thepivot member. A pivot member may be attached to the first housing andthe first core has an indentation to receive the pivot member. There maybe a gap between the first housing and the first core. The first housingmay have a semi-elliptical shape. A ratio of (i) a distance between thefulcrum point and an end of the first distal portion and (ii) a distancebetween the fulcrum point and an end of the first handle portion may beat least 5 to 1, 7 to 1, and the like. A maximum thickness of the firsthousing may be less than or equal to 11 millimeters. The currenttransformer may include a lock attached to the second handle portion andadapted to rotate about an axis, wherein the lock is adapted to rotateabout the axis into contact with the first handle portion preventingrotation of the first housing and the second housing about the fulcrumpoint. The lock may be made of plastic. The current transformer mayinclude a memory chip adapted to store a first scale factor of the firstcore and a second scale factor of the second core.

In accordance with an exemplary and non-limiting embodiment, a currentsensing device may include a current transformer for sensing a currentin an alternating current (AC) power line, the current transformerincluding a first housing including a first handle portion and a firstdistal portion; a second housing including a second handle portion and asecond distal portion; a first core having a first proximal core end anda first distal core end, the first core mounted in rotational contactwithin the first distal portion, wherein the first core is wrapped witha first conductor winding; and a second core having a second proximalcore end and a second distal core end, the second core mounted inrotational contact within the second distal portion, wherein the secondcore is wrapped with a second conductor winding; wherein the firsthousing is rotationally coupled to the second housing about a fulcrumpoint and wherein, when the first housing and the second housing arerotated into a closed position, the first core is adapted to rotatewithin the first distal portion and the second core is adapted to rotatewithin the second distal portion to enable contact between the firstproximal core end and the second proximal core end and to enable contactbetween the first distal core end and the second distal core end. Inembodiments, a pivot member may be attached to the first core and thefirst housing includes an indentation to receive the pivot member. Apivot member may be attached to the first housing and the first coreincludes an indentation to receive the pivot member. There may be a gapbetween the first housing and the first core. The first housing may havea semi-elliptical shape. A ratio of (i) a distance between the fulcrumpoint and an end of the first distal portion and (ii) a distance betweenthe fulcrum point and an end of the first handle portion may be 5 to 1,7 to 1, and the like. A maximum thickness of the first housing may beless than or equal to 11 millimeters. The current sensing device mayinclude a lock attached to the second handle portion and adapted torotate about an axis, wherein the lock is adapted to rotate about theaxis into contact with the first handle portion preventing rotation ofthe first housing and the second housing about the fulcrum point. Thecurrent sensing device may include a memory chip adapted to store afirst scale factor of the first core and a second scale factor of thesecond core.

In accordance with an exemplary and non-limiting embodiment, a currenttransformer assembly may include a first current transformer; a plug; afirst wire and a second wire between the plug and the first currenttransformer adapted to transmit a measurement of the first currenttransformer; and a memory chip adapted to store a first scale factor ofthe first current transformer. In embodiments, the memory chip may besituated inside the plug. The current transformer assembly may include athird wire between the plug and the memory chip, wherein the memory chipis connected to the second wire. The current transformer assembly mayinclude a third wire between the plug and the memory chip, and a fourthwire between the plug and the memory chip. The current transformerassembly may include a second current transformer, and a third wire anda fourth wire between the plug and the second current transformeradapted to transmit a measurement of the second current transformer, andwherein the memory chip is adapted to store a second scale factor of thesecond current transformer. The memory chip may be connected to thesecond wire and the fourth wire. The memory chip may be adapted to storea first scale factor of the first current transformer and a second scalefactor of the second current transformer.

In accordance with an exemplary and non-limiting embodiment, a systemmay include a current transformer assembly including a plug, a firstcurrent transformer, and a memory chip; a power monitor including atleast one processor and at least one memory, wherein the power monitoris configured to: read a first scale factor for the first currenttransformer from the memory chip, receive a first sensor value from thefirst current transformer, compute a second sensor value from the firstsensor value using the first scale factor, and use the second sensorvalue to determine information about energy consumption in a building.In embodiments, the memory chip may be situated inside the plug. Thepower monitor may read the first scale factor during a startup orinitialization process. The current transformer assembly may furtherinclude a first wire and a second wire between the plug and the firstcurrent transformer, wherein the memory chip is connected to at leastone of the first wire and the second wire. The current transformerassembly may further include a second current transformer, wherein thepower monitor is further configured to: read a second scale factor forthe second current transformer from the memory chip, receive a thirdsensor value from the second current transformer, compute a fourthsensor value from the third sensor value using the second scale factor,and use the second sensor value and the fourth sensor value to determineinformation about energy consumption in the building. The currenttransformer assembly may further include a first wire and a second wirebetween the plug and the first current transformer, a third wire and afourth wire between the plug and the second current transformer, whereinthe memory chip is connected to at least one of the first wire, secondwire, third wire, and fourth wire. The memory chip may be connected tothe second wire and the fourth wire.

In accordance with an exemplary and non-limiting embodiment, a methodfor calibrating a current transformer may include reading a first scalefactor for a first current transformer from a memory chip, receiving afirst sensor value from the first current transformer, computing asecond sensor value from the first sensor value using the first scalefactor, and using the second sensor value to determine currentinformation. In embodiments, reading the first scale factor may beperformed during a startup or initialization process. The informationabout energy consumption in the building may include information aboutat least a first electrical power consuming device and a secondelectrical power consuming device in the building. The method mayfurther include reading a second scale factor for a second currenttransformer from the memory chip, receiving a third sensor value fromthe second current transformer, computing a fourth sensor value from thethird sensor value using the second scale factor, and using the secondsensor value and the fourth sensor value to determine information aboutenergy consumption in the building. The first scale factor may be afirst calibration factor for the first current transformer and thesecond scale factor may be a second calibration factor for the secondcurrent transformer. The method may further include reading a currenttransformer identifier from the memory chip.

In accordance with an exemplary and non-limiting embodiment, a currenttransformer may include a first semi-elliptical housing including afirst handle portion and a first distal portion, a secondsemi-elliptical housing including a second handle portion and a seconddistal portion, a first core having a first proximal core end and afirst distal core end the first core mounted in rotational contactwithin the first distal portion and a second core having a secondproximal core end and a second distal core end the second core mountedin rotational contact within the second distal portion wherein the firstsemi-elliptical housing is rotationally coupled to the secondsemi-elliptical housing about a fulcrum point. In embodiments, a ratioof (i) a distance between the fulcrum point and an end of the firstdistal portion and (ii) a distance between the fulcrum point and an endof the first handle portion may be at least 5 to 1, 7 to 1, and thelike. A maximum thickness of the first semi-elliptical housing is lessthan or equal to 9 millimeters, 11 millimeters, 13 millimeters, and thelike.

In accordance with an exemplary and non-limiting embodiment, a currenttransformer may include a first housing having a first handle portionand a first distal portion, a second housing having a second handleportion and a second distal portion, a first core having a firstproximal core end and a first distal core end the first core mountedwithin the first distal portion, a second core having a second proximalcore end and a second distal core end the second core mounted within thesecond distal portion; and a lock attached to the second handle portionand adapted to rotate about an axis, wherein the first housing isrotationally coupled to the second housing about a fulcrum point andwherein the lock is adapted to rotate about the axis into contact withthe first handle portion preventing rotation of the first housing andthe second housing about the fulcrum point. In embodiments, the firstcore may be mounted in rotational contact within the first distalportion and the second core is mounted in rotational contact within thesecond distal portion. The lock may be made of plastic. The firsthousing and or the second housing may have a semi-elliptical shape.

In accordance with an exemplary and non-limiting embodiment, a currenttransformer may include a first housing having a first handle portion, afirst distal portion and a cylindrical first hinge portion, a secondhousing having a second handle portion, a second distal portion and acylindrical second hinge portion, a first core having a first proximalcore end and a first distal core end the first core mounted within thefirst distal portion, a second core having a second proximal core endand a second distal core end the second core mounted within the seconddistal portion; and a spring; and a hinge including the cylindricalfirst hinge portion, the cylindrical second hinge portion, and thespring, wherein the cylindrical first hinge portion in rotationalcontact with the cylindrical second hinge portion about which ispositioned the spring, the spring adapted to produce a rotational forcebetween the first housing and the second housing. In embodiments, acenter of a coil of the spring may be located at a fulcrum of the hinge.A coil of the spring may be located within the cylindrical first hingeportion and the cylindrical second hinge portion.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary and non-limiting embodiment of a currenttransformer in a closed position.

FIG. 2 illustrates an exemplary and non-limiting embodiment of a currenttransformer in an open position with covers removed.

FIG. 3A illustrates an exemplary and non-limiting embodiment of anexploded view of a current transformer.

FIG. 3B illustrates an exemplary and non-limiting embodiment of anisometric view of a current transformer.

FIG. 4A illustrates an exemplary and non-limiting embodiment of acircuit diagram.

FIG. 4B illustrates an exemplary and non-limiting embodiment of acircuit diagram.

FIG. 4C illustrates an exemplary and non-limiting embodiment of acircuit diagram.

FIG. 5 illustrates an exemplary and non-limiting embodiment of a distalend of a current transformer.

FIG. 6 illustrates an exemplary and non-limiting embodiment of anexploded view of a current transformer.

FIG. 7 illustrates an exemplary and non-limiting embodiment of a plugand cord for a current transformer assembly.

DETAILED DESCRIPTION

A power monitor may be installed in a building to obtain informationabout power usage within the building. For example, a power monitor maybe installed in a conventional electrical panel, may be part of a smartelectrical panel, or may be part of a smart electrical meter. A powermonitor may determine information about power consumption by usingsensors that measure an electrical property of the power mains (e.g.,alternating current (AC) power line) that provide power to the buildingor an electrical property of power generated by solar panels. Forexample, where a building has two power mains, a power monitor may havea sensor (e.g., a current sensing device) for each of the two mains. Insome embodiments, the sensors of a power monitor may include a currenttransformer, such as any of the current transformers described herein. Apower monitor may have any of the characteristics of power monitors asdescribed in U.S. Pat. Nos. 9,443,195; 9,699,529; or U.S. Pat. No.10,586,177, each of which are incorporated herein by reference in theirentireties.

With reference to FIG. 1, there is illustrated an exemplary andnon-limiting embodiment of a current transformer 100. Currenttransformer 100 includes in part a clamp formed of a semi-ellipticalfirst housing 102 and a semi-elliptical second housing 104. Firsthousing 102 is formed of first handle portion 108 and first distalportion 110. Likewise, second housing 104 is formed of second handleportion 112 and second distal portion 114. First distal portion 110extends and terminates at first housing terminus 118 while second distalportion 114 extends and terminates at second housing terminus 122, suchas including a mating portion 120 to reduce misalignment.

First housing 102 and second housing 104 rotate axially about fulcrumpoint 106. Fulcrum point 106 defines, generally, the division betweenthe second handle portion 112 and second distal portion 114 of secondhousing 104. Fulcrum point 106 similarly defines, generally, thedivision between the first handle portion 108 and first distal portion110 of first housing 102. As described more fully below, an internalspring situated around the fulcrum point 106 provides rotational forceto each of the first housing 102 and second housing 104 so as to renderthe current transformer 100 in a closed state with a first housingterminus 118 in contact with a second housing terminus 122.

As configured, an operator of current transformer 100 may squeeze, withone hand, first handle portion 108 and second handle portion 112 towardsone another resulting in a rotation of the first housing 102 and secondhousing 104 about fulcrum point 106 and separating first housingterminus 118 from second housing terminus 122.

First housing terminus 118 and second housing terminus 122 may be thusseparated a distance sufficient greater than or equal to a diameter ofan electrical main. As a result, when first handle portion 108 andsecond handle portion 112 are squeezed so as to separate the firsthousing terminus 118 from second housing terminus 122, an electricalmain may be slid into the gap so formed at which point the pressureapplied to first handle portion 108 and second handle portion 112 may bereleased. Releasing the pressure applied to first handle portion 108 andsecond handle portion 112 causes the current transformer 100 to returnto a closed state whereby the electrical main is secured between firstdistal portion 110 and second distal portion 114.

Fulcrum point 106 divides the longitudinal extent of current transformer100 into a proximal distance d1 and a distal distance d2. The ratio ofd1 to d2 may be between 1:5 and 1:8, preferably approximately 1:7. Aratio of 1:7 allows for a distance d1 that is sufficiently small toallow for a user to open the current transformer 100 with one hand.These ratios produce a reduced end-to-end length of the currenttransformer 100 that allows the maximum oval area for engagement with areduced handle size so as to fit into tight places. The ratio allows asmaller handle while enabling single hand installation due to low springforce and design features of the hinge. In some embodiments, first andsecond housings 102, 104 are formed of plastic material and have anoverall thickness of approximately 11 millimeters (mm), which may bethinner than conventional current transformers. The thickness of thewalls of the plastic housing may nevertheless be sufficient to meet theUL94 V-0 flame retardant rating.

Connector 116 may provide electrical signals to and from currenttransformer 100. In one embodiment, connector 116 transmits a signalgenerated by the current transformer 100 resulting from electricalcurrent passing through an electrical main.

With reference to FIG. 2, there is illustrated an exemplary andnon-limiting embodiment of current transformer 100 in a cutaway viewshowing the internal geometry and construction of current transformer100. Housed within first distal portion 110 is core 204. Cores 204, 206may be fabricated of a ferrite homogeneous material (providing lowperformance, lowest cost) and/or a homogeneous iron cores (providing midperformance, mid cost), or iron cores made from laminated sheets(providing highest performance, highest cost). In addition, there areseveral grades of silicon iron cores that may be employed. In someembodiments, there may be employed a silicon iron core that is laminatedin sheets to create the structure having, for example, a reduced crosssectional area being approximately 3.5 mm×7.5 mm adapted to produce asmall geometry with the maximum flux saturation for best performance.

Similarly, housed within second distal portion 114 is core 206. Core 204is surrounded along a sizeable portion of its length by winding 200.Core 206 is surrounded along a sizeable portion of its length by winding202. Note that both of core 204 and winding 200 fit inside the walls offirst distal portion 110 such that gaps 208, 208′ exist on either sideof core 204 and winding 200 between the walls forming first distalportion 110. Similarly, core 206 and winding 202 fit inside the walls ofsecond distal portion 114 such that gaps 210, 210′ exist on either sideof core 206 and winding 202 between the walls forming second distalportion 114.

Extending through core 204 and winding 200 is pivot member 212. Pivotmember 212 is generally cylindrical in shape and is adapted such thatopposing ends of pivot member 212 may by inserted into reciprocatingholes or indentations 312 (as illustrated in FIG. 3A) fabricated intothe walls of first distal portion 110 so as to allow core 204 andwinding 200 to rotate about pivot member 212 as indicated within firstdistal portion 110 and as provided by gaps 208, 208′. In an alternateembodiment, pivot member 212 may be attached to the surface of core 204.Conversely, in an alternate embodiment, one or more pivot members may befabricated as part of the first and second distal portions with suchpivot members engaging with one or more holes or indentations fabricatedas part of cores 204, 206 or in a casing enclosing cores 204, 206.

Extending through core 206 and winding 202 is pivot member 214. Pivotmember 214 is generally cylindrical in shape and is adapted such thatopposing ends of pivot member 214 may by inserted into reciprocatingholes 314 (as illustrated in FIG. 3A) fabricated into the walls ofsecond distal portion 114 so as to allow core 206 and winding 202 torotate about pivot member 214 as indicated within second distal portion114 and as provided by gaps 210, 210′.

When in a closed position, first proximal core end 216 comes intocontact with second proximal core end 220. Similarly, first distal coreend 218 comes into contact with second distal core end 222. By allowingeach of cores 204, 206 to rotate about corresponding pivot members 212,214, each core 204, 206 is adapted to rotate into a position wherebyfirst distal core end 218 rests in contact with second distal core end222 and first proximal core end 216 rests in contact with secondproximal core end 220. Without the ability of cores 204, 206 to rotateabout corresponding pivot members 212, 214, the contacts between thedistal core ends and/or the proximal core ends may be incomplete orinsufficient, and thus reducing the accuracy of the current transformer.

An advantage of the configuration of current transformer 100 is that theamount of force applied by spring 306 to close the clamp may be reduced.The reduced force of spring 306 allows for easier opening of the clampby an operator using only one hand. The configuration of the currenttransformer allows a reduced force spring to provide sufficient matingand contact between the ends of core 204 and core 206.

With continued reference to FIG. 1, lock 124 extends from second handleportion 112 and is axially connected thereto so as to rotate about pivotpoint 126. As noted above, FIG. 1 shows the current transformer 100 in aclosed position. When in such a position, lock 124 may be rotatedaxially about pivot point 126 to engage with first handle portion 108 soas to prevent either first handle portion 108 or second handle portion112 from moving towards one another when squeezed by a user. Engaginglock 124 ensures that the two halves of the cores 204, 206, achieve andmaintain solid contact with each other. Lock 124 further ensures thatwhen a panel of a cabinet in which the current transformer 100 is housedis closed, neither the panel nor other components will force the currenttransformer 100 to open. As illustrated, the lock 124 closing action isin the desired direction to mechanically wedge the assembly closed.

The lock 124 may provide a tactile and audible feedback that it isengaged. The lock 124 is designed to “CAM” away when the currenttransformer 100 is being opened, to avoid any cumbersome motion to pullit away while opening the current transformer for installation, in anydirection. The lock is further designed to be locked with one hand andunlocked with one hand, keeping the hand from any area with a liveconductor. As a result, current transformer 100 complies, generally,with industry standard IEC61010-2-032 directed to hand held and handmanipulated parts whereat a hand held part is defined as a part intendedto be supported by one hand during normal use. More specifically,IEC61010-2-032 defines a type A current sensor as: “ . . . a currentsensor designed to be applied around or removed from UNINSULATEDHAZARDOUS LIVE conductors. Type A current sensors have defined HAND-HELDor hand-manipulated parts providing protection against electric shockfrom the conductor being measured, and also have protection againstshort-circuits between wires and busbars during clamping”. The lock maybe constructed of any appropriate material, such as plastic.

With reference to FIG. 3A, there is illustrated an exemplary andnon-limiting embodiment of an exploded view of current transformer 100.Current transformer is designed to be relatively thin, preferably lessthan 11 mm front to back, to facilitate operation in confinedenvironments. This requirement for thinness of the current transformer100 limits the amount of plastic available for a secure hinge. In theillustrated embodiment, first hinge portion 302 is adapted to beinserted in rotational contact with second hinge portion 304 forming ahinge providing rotation of first housing 102 and second housing 104about fulcrum point 106. The concentric circle style hinge is formed byconcentrically located first hinge portion 302 and second hinge portion304. The concentric style hinge provides sufficient support for rotatingthe first housing 102 with respect to second housing 104 despite therelatively thin nature of the housings. The concentric style hinge mayalso reduce any misalignment of first housing 102 with respect to secondhousing 104 across all three axes and thus improve mating and contactbetween the ends of core 204 and core 206.

Each of first hinge portion 302 and second hinge portion 304 may be inthe shape of a portion of a cylinder. An outer surface of first hingeportion 302 may be in contact with an inner surface of second hingeportion 304. When the current transformer is opened or closed, thesurfaces of first hinge portion 302 and second hinge portion 304 mayrotate against one another. The cylindrical and concentric constructionof the hinge provides a larger surface area than conventional hinges andthus provides more physical support for the hinge. First hinge portion302 and second hinge portion 304 may be constructed of any appropriatematerial, such as plastic.

The top covers of first housing 102 and second housing 104 may havecomplementary features to mate with first hinge portion 302 and secondhinge portion 304. These complementary features may engage with thefirst hinge portion 302 and second hinge portion 304 to reduce anymisalignment of first housing 102 with respect to second housing 104across all three axes and thus improve mating and contact between theends of core 204 and core 206.

The spring 306 may be concentric to the hinge and may be, for example, atorsion spring. In some embodiments, a center point of the coil of thespring 306 may be located at the fulcrum of the hinge. In someembodiments, the coil of the spring 306 may be inside both first hingeportion 302 and second hinge portion 304 and one or more legs of thespring may extend through first hinge portion 302 and/or second hingeportion 304 to provide resistance when the clamp is opened. Where thecoil of spring 306 is inside hinge portion 302 and second hinge portion304, greater separation may be achieved between the live wires of thetransformer and the metal of the spring (isolating live parts from deadmetal), and the separation may provide for increased safety of thecurrent transformer. This configuration may provide increased dielectricisolation of the spring from live parts and assist with compliance withUL 2808. The top cover of first housing 102 interlocks with second hingeportion 304 to provide a wire path for the wires connected to winding202, and the top cover of second housing 104 interlocks with first hingeportion 302 to provide a wire path for the wires connected to winding200. The interlocks also prevent the wires from coming in contact withdead metal, such as spring 306. FIG. 3B illustrates an exemplary andnon-limiting embodiment of an isometric view of a current transformer.

With further reference to FIG. 3A, reciprocating holes or indentations312 are illustrated to allow core 204 and winding 200 to rotate aboutpivot member 212 (second pivot member hidden from view), andreciprocating holes or indentations 314 are illustrated to allow core206 and winding 202 to rotate about pivot member 214 (second pivotmember hidden from view).

With reference to FIG. 4A, there is illustrated an exemplary andnon-limiting embodiment of a circuit diagram of a current transformerassembly including two current transformers 100, 100′ that is connectedto a current transformer interface 410 through a connection interface460 (e.g., a multi-wire cable with plug for connecting to the currenttransformer interface). The current transformer interface 410 may beused to interface with the current transformer assembly to obtain sensorreadings (e.g., by a power monitoring device) or to configure thecurrent transformer assembly, as described in greater detail below. Inembodiments, the current transformer interface 410 may be integratedinto or represent the power monitor as described, where the terms“current transformer interface” and “power monitor” may be usedinterchangeably herein.

As illustrated, a memory chip 400, is attached to existing negativewires 464 464′ of each current transformer 100, 100′, and thus, in someembodiments, may not require any additional wires (e.g., as providedthrough the connector interface 460) to accommodate connection to thememory chip 400. Memory chip 400 may use any appropriate techniques forstoring data, such as a volatile memory chip, a non-volatile memorychip, an EEPROM (electrically erasable programmable read-only memory),or EPROM (erasable programmable read-only memory). In some embodiments,positive wires 462 462′ may be utilized instead of negative wires 464464′ or both negative and positive wires may be utilized (e.g., negativewire 464′ and positive wire 462′. In a non-limiting example, the memorychip 400 may be connected to the two wires of a current transformer 100,one wire of the current transformer 100 and one wire of the currenttransformer 100′, or two wires of a current transformer 100′.

In use, different current transformers may differ one from another intheir sensitivity. As a result, two different current transformers 100making a reading of the same electrical main may differ slightly. Priorto use, during a calibration process, a scale factor is computed foreach of the two current transformers 100, 100′ and stored on the memorychip 400. When the current transformers are used with a power monitor,the power monitor may obtain the scale factors for the currenttransformers from memory chip 400, and use the scale factors to obtainmore accurate readings from the current transformers. For example, atrue current being measured may be 8 amps. A first current transformermay indicate a current value of 10 amps. The scale factor stored onmemory chip 400 for the first current transformer may allow the powermonitor to correct the signal received from the first currenttransformer to determine that the current is actually 8 amps. Forexample, the scale factor may indicate to adjust the signal or a valuereceived from the first current transformer downwards by a factor of 0.2or 20%. The power monitor may then compute an adjusted value using thescale factor and use the adjusted value for determining informationabout energy consumption for one or more electrical power consumingdevices in a building (such as any of the information described in theincorporated patents and applications).

As a result, if a new pair of current transformers 100, 100′ is swappedwith an existing pair of an assembly, the scale factors of each newcurrent transformer 100, 100′ may be read and utilized such that inputgathered from the newly swapped current transformers 100, 100′ do notdiffer in scale from the previously used current transformers.

In some embodiments, the power monitor may read the scale factors frommemory chip 400 during a startup or initialization process. In someembodiments, the power monitor may read the scale factors wheninstructed to do so (e.g., from a server computer in communication withthe power monitor) or on a periodic basis. In some embodiments, thememory chip may be connected to the existing wires (e.g., negativewires) of the current transformer assembly. Similar chips used in Macpower cords use additional wires or contact points while the presentembodiment reuses existing wires and connector pins, thus reducing theconnector size without interfering with the operation of the currenttransformer.

In addition to the stored scaling factor, the memory chip 400 may storeidentifying information related to each current transformer in the formof a current transformer identifier (CTID). This identifier mayindicate, for example, a date code, date of manufacture, or a locationof manufacture. The ability to store and retrieve information indicativeof a unique current transformer 100 decreases repair costs, increasesaccuracy, and makes installation easier. In addition, installation iseasier as there is no need to match a current transformer to a unitjack. Further, product support is reduced as mis-installed currenttransformers may result in support calls about inaccuracy. Repair costsare further reduced as there is no need to replace a power monitor andcurrent transformers as a unit—just the failing component.

With reference to FIG. 4A, current transformer interface 410 may be usedto obtain sensor readings from the current transformer, read the scalefactors from memory chip 400, or write the scale factors to memory chip400. For example, a power monitor may include current transformerinterface 410 or a calibration device may include current transformerinterface 410.

Current transformer interface 410 may include analog-to-digitalconverter (A/D) 420. A/D 420 may receive analog signals from the currenttransformers and produce a sequence of digital values (currenttransformer data or CT data) for further processing.

Current transformer interface 410 may include system on a chip (SoC) 430that may receive the CT data from A/D 420. SoC 430 may furthercoordinate in receiving sensor data from the current transformers andreading or writing scale factors from memory chip 400. SoC 430 mayinclude an enable pin or output that switches the current transformerinterface 410 between reading sensor data and reading or writing scalefactors. In some embodiments, the enable output may be connected to amultiplexor circuit, such as multiplexors 450, 450′. For example, wherethe enable output is 0, the multiplexors may be configured to sendsensor data to A/D 420, and where the enable output is 1, themultiplexors may be configured to assist with reading from or writing tomemory chip 400.

Current transformer interface 410 may include power and interface (I/F)circuit 440 to assist with reading from or writing to memory chip 400.For example, power and I/F circuit 440 may provide the power needed toperform a read or write operation and an interface to convert the scalefactors stored on memory chip 400 into a format to be used by SoC 430.

With reference to FIG. 4B, there is illustrated an exemplary andnon-limiting embodiment of a circuit diagram of a current transformerassembly illustrating a first connection to the memory chip 400 attachedto an existing negative wire 464′ of the current transformer 100′ and asecond connection 470 to the memory chip 400 to the power and I/Fcircuit 440. In some embodiments, a positive wire may be utilizedinstead of negative wire for the first connection. In a non-limitingexample, the current transformer interface 410 may be used to interfacewith the current transformer assembly 100′ to obtain sensor readings orto configure the current transformer assembly through a first connection462′ and second connection 464′, and the memory chip 400 is attached tothe power and I/F circuit 440 by one of the first or second connections(e.g., negative wire connection 464′, or in embodiments any of the wiredconnections to the current transformers 100 100′) and by a third wire470. Thus, the memory chip 400 would share one of the existing wireconnections to the current transformers 100 100′ and utilize anadditional wired connection 470 to accommodate connectivity with thememory chip 400. As such, the wired connections through the connectioninterface 460 to the current transformer 100′ and the memory chip 400may include three wires (e.g., in addition to the two wires for thecurrent transformer 100).

With reference to FIG. 4C, there is illustrated an exemplary andnon-limiting embodiment of a circuit diagram of a current transformerassembly illustrating a first connection to the memory chip 400 attachedto the power and I/F circuit 440 and a second connection to the memorychip 400 attached to a common connection point of the currenttransformer interface 410. In a non-limiting example, the currenttransformer interface 410 may be used to interface with the currenttransformer assembly 100′ to obtain sensor readings or to configure thecurrent transformer assembly through a first wire connection 462′ andsecond wire connection 464′, and the memory chip 400 is attached to thepower and I/F circuit 440 by dedicated third connection wire 470 andfourth connection wire 480. Thus, the connections to the memory chip 400may be independent of connections to the current transformers 100 100′.As such, the wired connections through the connection interface 460 tothe current transformer 100′ and the memory chip 400 may include fourwires (e.g., in addition to the two wires for the current transformer100).

With reference to FIG. 5, there is illustrated an exemplary andnon-limiting embodiment of the distal end of a current transformer 100.As shown, two opposing distal ends 500, 502 are in contact with eachother when the current transformer 100 in a closed position. Note thatdistal end 502 is tapered or dimpled with respect to opposing distal end500. This reduced nose area of distal end 502 allows for a reducedheight in this region to provide for increased manipulation andorientation in consumer electrical panels. With the core shape and ovaldesign, the current transformer windings may be kept away from thisregion allowing the plastic shell to be reduced and create thisadvantageous shape. The interlocking nose pieces provide a shield toprevent exposing this inner core and their windings. In some instances,the tapering accommodates a known barrier/obstruction commonly presentin electrical panels and/or solar junction panels.

With reference to FIG. 6, there is disclosed an alternative embodimentfor the hinge within the current transformer 100. In the illustratedembodiment, first hinge portion 602 is adapted to be inserted inrotational contact with second hinge portion 604 forming a hingeproviding rotation of first housing 102 and second housing 104 aboutfulcrum point 106. The concentric circle style hinge is formed byconcentrically located first hinge portion 602 and second hinge portion604. In the embodiment of FIG. 6, the coil of spring 606 may be outsideboth first hinge portion 602 and second hinge portion 604.

With reference to FIG. 7, there is disclosed an exemplary andnon-limiting embodiment of a plug and cord 700 for implementation of thecurrent interface 460 of a current transformer assembly. Plug 702 may beadapted to be plugged into a power monitor. First connection 704 may beconnected to a first current transformer 100 (not shown) through wires462, 464, and second connection 704′ may be connected to a secondcurrent transformer 100′ (not shown) through wires 462′, 464′. In someembodiments, a current transformer assembly may have a single currenttransformer (and thus a single cord and connection, e.g., 462, 464), andin some embodiments, a current transformer assembly may have more thantwo current transformers (and thus more than two cords and connections462, 464, 462′, 464′). Where a current transformer assembly includesmemory chip 400, memory chip 400 may be situated in any appropriatelocation. In some embodiments, memory chip 400 may be situated withinthe plug 702. As described herein, the memory chip 400 may connect tosome combination of the existing connections 462, 464, 462′, 464′ of thecurrent transformers 100, 100′, to one of the existing connections 462,464, 462′, 464′ of the current transformers 100, 100′ and an additionaldedicated connection 470 (additional wire not shown), or to dedicatedconnections 470, 480 (additional wires not shown).

While only a few embodiments of the present disclosure have been shownand described, it will be obvious to those skilled in the art that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the present disclosure as described in thefollowing claims. All patent applications and patents, both foreign anddomestic, and all other publications referenced herein are incorporatedherein in their entireties to the full extent permitted by law.

The methods and systems described herein may be deployed in part or inwhole through a machine that executes computer software, program codes,and/or instructions on a processor. The present disclosure may beimplemented as a method on the machine, as a system or apparatus as partof or in relation to the machine, or as a computer program productembodied in a computer readable medium executing on one or more of themachines. In embodiments, the processor may be part of a server, cloudserver, client, network infrastructure, mobile computing platform,stationary computing platform, or other computing platform. A processormay be any kind of computational or processing device capable ofexecuting program instructions, codes, binary instructions and the like.The processor may be or may include a signal processor, digitalprocessor, embedded processor, microprocessor or any variant such as aco-processor (math co-processor, graphic co-processor, communicationco-processor and the like) and the like that may directly or indirectlyfacilitate execution of program code or program instructions storedthereon. In addition, the processor may enable execution of multipleprograms, threads, and codes. The threads may be executed simultaneouslyto enhance the performance of the processor and to facilitatesimultaneous operations of the application. By way of implementation,methods, program codes, program instructions and the like describedherein may be implemented in one or more thread. The thread may spawnother threads that may have assigned priorities associated with them;the processor may execute these threads based on priority or any otherorder based on instructions provided in the program code. The processor,or any machine utilizing one, may include non-transitory memory thatstores methods, codes, instructions and programs as described herein andelsewhere. The processor may access a non-transitory storage mediumthrough an interface that may store methods, codes, and instructions asdescribed herein and elsewhere. The storage medium associated with theprocessor for storing methods, programs, codes, program instructions orother type of instructions capable of being executed by the computing orprocessing device may include but may not be limited to one or more of aCD-ROM, DVD, memory, hard disk, flash drive, RAM, ROM, cache and thelike.

A processor may include one or more cores that may enhance speed andperformance of a multiprocessor. In embodiments, the process may be adual core processor, quad core processors, other chip-levelmultiprocessor and the like that combine two or more independent coresto provide speed improvements.

The methods and systems described herein may be deployed in part or inwhole through a machine that executes computer software on a server,client, firewall, gateway, hub, router, or other such computer and/ornetworking hardware. The software program may be associated with aserver that may include a file server, print server, domain server,internet server, intranet server, cloud server, and other variants suchas secondary server, host server, distributed server and the like. Theserver may include one or more of memories, processors, computerreadable media, storage media, ports (physical and virtual),communication devices, and interfaces capable of accessing otherservers, clients, machines, and devices through a wired or a wirelessmedium, and the like. The methods, programs, or codes as describedherein and elsewhere may be executed by the server. In addition, otherdevices required for execution of methods as described in thisapplication may be considered as a part of the infrastructure associatedwith the server.

The server may provide an interface to other devices including, withoutlimitation, clients, other servers, printers, database servers, printservers, file servers, communication servers, distributed servers,social networks, and the like. Additionally, this coupling and/orconnection may facilitate remote execution of program across thenetwork. The networking of some or all of these devices may facilitateparallel processing of a program or method at one or more locationwithout deviating from the scope of the disclosure. In addition, any ofthe devices attached to the server through an interface may include atleast one storage medium capable of storing methods, programs, codeand/or instructions. A central repository may provide programinstructions to be executed on different devices. In thisimplementation, the remote repository may act as a storage medium forprogram code, instructions, and programs.

The software program may be associated with a client that may include afile client, print client, domain client, internet client, intranetclient and other variants such as secondary client, host client,distributed client and the like. The client may include one or more ofmemories, processors, computer readable media, storage media, ports(physical and virtual), communication devices, and interfaces capable ofaccessing other clients, servers, machines, and devices through a wiredor a wireless medium, and the like. The methods, programs, or codes asdescribed herein and elsewhere may be executed by the client. Inaddition, other devices required for execution of methods as describedin this application may be considered as a part of the infrastructureassociated with the client.

The client may provide an interface to other devices including, withoutlimitation, servers, other clients, printers, database servers, printservers, file servers, communication servers, distributed servers andthe like. Additionally, this coupling and/or connection may facilitateremote execution of program across the network. The networking of someor all of these devices may facilitate parallel processing of a programor method at one or more location without deviating from the scope ofthe disclosure. In addition, any of the devices attached to the clientthrough an interface may include at least one storage medium capable ofstoring methods, programs, applications, code and/or instructions. Acentral repository may provide program instructions to be executed ondifferent devices. In this implementation, the remote repository may actas a storage medium for program code, instructions, and programs.

The methods and systems described herein may be deployed in part or inwhole through network infrastructures. The network infrastructure mayinclude elements such as computing devices, servers, routers, hubs,firewalls, clients, personal computers, communication devices, routingdevices and other active and passive devices, modules and/or componentsas known in the art. The computing and/or non-computing device(s)associated with the network infrastructure may include, apart from othercomponents, a storage medium such as flash memory, buffer, stack, RAM,ROM and the like. The processes, methods, program codes, instructionsdescribed herein and elsewhere may be executed by one or more of thenetwork infrastructural elements. The methods and systems describedherein may be adapted for use with any kind of private, community, orhybrid cloud computing network or cloud computing environment, includingthose which involve features of software as a service (SaaS), platformas a service (PaaS), and/or infrastructure as a service (IaaS).

The methods, program codes, and instructions described herein andelsewhere may be implemented on a cellular network has sender-controlledcontact media content item multiple cells. The cellular network mayeither be frequency division multiple access (FDMA) network or codedivision multiple access (CDMA) network. The cellular network mayinclude mobile devices, cell sites, base stations, repeaters, antennas,towers, and the like. The cell network may be a GSM, GPRS, 3G, EVDO,mesh, or other networks types.

The methods, program codes, and instructions described herein andelsewhere may be implemented on or through mobile devices. The mobiledevices may include navigation devices, cell phones, mobile phones,mobile personal digital assistants, laptops, palmtops, netbooks, pagers,electronic books readers, music players and the like. These devices mayinclude, apart from other components, a storage medium such as a flashmemory, buffer, RAM, ROM and one or more computing devices. Thecomputing devices associated with mobile devices may be enabled toexecute program codes, methods, and instructions stored thereon.Alternatively, the mobile devices may be configured to executeinstructions in collaboration with other devices. The mobile devices maycommunicate with base stations interfaced with servers and configured toexecute program codes. The mobile devices may communicate on apeer-to-peer network, mesh network, or other communications network. Theprogram code may be stored on the storage medium associated with theserver and executed by a computing device embedded within the server.The base station may include a computing device and a storage medium.The storage device may store program codes and instructions executed bythe computing devices associated with the base station.

The computer software, program codes, and/or instructions may be storedand/or accessed on machine readable media that may include: computercomponents, devices, and recording media that retain digital data usedfor computing for some interval of time; semiconductor storage known asrandom access memory (RAM); mass storage typically for more permanentstorage, such as optical discs, forms of magnetic storage like harddisks, tapes, drums, cards and other types; processor registers, cachememory, volatile memory, non-volatile memory; optical storage such asCD, DVD; removable media such as flash memory (e.g. USB sticks or keys),floppy disks, magnetic tape, paper tape, punch cards, standalone RAMdisks, Zip drives, removable mass storage, off-line, and the like; othercomputer memory such as dynamic memory, static memory, read/writestorage, mutable storage, read only, random access, sequential access,location addressable, file addressable, content addressable, networkattached storage, storage area network, bar codes, magnetic ink, and thelike.

The methods and systems described herein may transform physical and/oror intangible items from one state to another. The methods and systemsdescribed herein may also transform data representing physical and/orintangible items from one state to another.

The elements described and depicted herein, including in flow charts andblock diagrams throughout the figures, imply logical boundaries betweenthe elements. However, according to software or hardware engineeringpractices, the depicted elements and the functions thereof may beimplemented on machines through computer executable media hassender-controlled contact media content item a processor capable ofexecuting program instructions stored thereon as a monolithic softwarestructure, as standalone software modules, or as modules that employexternal routines, code, services, and so forth, or any combination ofthese, and all such implementations may be within the scope of thepresent disclosure. Examples of such machines may include, but may notbe limited to, personal digital assistants, laptops, personal computers,mobile phones, other handheld computing devices, medical equipment,wired or wireless communication devices, transducers, chips,calculators, satellites, tablet PCs, electronic books, gadgets,electronic devices, devices has sender-controlled contact media contentitem artificial intelligence, computing devices, networking equipment,servers, routers and the like. Furthermore, the elements depicted in theflow chart and block diagrams or any other logical component may beimplemented on a machine capable of executing program instructions.Thus, while the foregoing drawings and descriptions set forth functionalaspects of the disclosed systems, no particular arrangement of softwarefor implementing these functional aspects should be inferred from thesedescriptions unless explicitly stated or otherwise clear from thecontext. Similarly, it will be appreciated that the various stepsidentified and described above may be varied, and that the order ofsteps may be adapted to particular applications of the techniquesdisclosed herein. All such variations and modifications are intended tofall within the scope of this disclosure. As such, the depiction and/ordescription of an order for various steps should not be understood torequire a particular order of execution for those steps, unless requiredby a particular application, or explicitly stated or otherwise clearfrom the context.

The methods and/or processes described above, and steps associatedtherewith, may be realized in hardware, software or any combination ofhardware and software suitable for a particular application. Thehardware may include a general-purpose computer and/or dedicatedcomputing device or specific computing device or particular aspect orcomponent of a specific computing device. The processes may be realizedin one or more microprocessors, microcontrollers, embeddedmicrocontrollers, programmable digital signal processors or otherprogrammable device, along with internal and/or external memory. Theprocesses may also, or instead, be embodied in an application specificintegrated circuit, a programmable gate array, programmable array logic,or any other device or combination of devices that may be configured toprocess electronic signals. It will further be appreciated that one ormore of the processes may be realized as a computer executable codecapable of being executed on a machine-readable medium.

The computer executable code may be created using a structuredprogramming language such as C, an object oriented programming languagesuch as C++, or any other high-level or low-level programming language(including assembly languages, hardware description languages, anddatabase programming languages and technologies) that may be stored,compiled or interpreted to run on one of the above devices, as well asheterogeneous combinations of processors, processor architectures, orcombinations of different hardware and software, or any other machinecapable of executing program instructions.

Thus, in one aspect, methods described above and combinations thereofmay be embodied in computer executable code that, when executing on oneor more computing devices, performs the steps thereof. In anotheraspect, the methods may be embodied in systems that perform the stepsthereof, and may be distributed across devices in a number of ways, orall of the functionality may be integrated into a dedicated, standalonedevice or other hardware. In another aspect, the means for performingthe steps associated with the processes described above may include anyof the hardware and/or software described above. All such permutationsand combinations are intended to fall within the scope of the presentdisclosure.

While the disclosure has been disclosed in connection with the preferredembodiments shown and described in detail, various modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present disclosure isnot to be limited by the foregoing examples, but is to be understood inthe broadest sense allowable by law.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosure (especially in the context of thefollowing claims) is to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “has sender-controlled contact mediacontent item,” “including,” and “containing” are to be construed asopen-ended terms (i.e., meaning “including, but not limited to,”) unlessotherwise noted. Recitation of ranges of values herein are merelyintended to serve as a shorthand method of referring individually toeach separate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated into the specificationas if it were individually recited herein. All methods described hereincan be performed in any suitable order unless otherwise indicated hereinor otherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the disclosure and does not pose alimitation on the scope of the disclosure unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the disclosure.

While the foregoing written description enables one of ordinary skill tomake and use what is considered presently to be the best mode thereof,those of ordinary skill will understand and appreciate the existence ofvariations, combinations, and equivalents of the specific embodiment,method, and examples herein. The disclosure should therefore not belimited by the above described embodiment, method, and examples, but byall embodiments and methods within the scope and spirit of thedisclosure.

All documents referenced herein are hereby incorporated by reference.

What is claimed is:
 1. A current transformer assembly comprising: afirst current transformer; a plug; a first wire and a second wirebetween the plug and the first current transformer adapted to transmit ameasurement of the first current transformer; and a memory chip adaptedto store a first scale factor of the first current transformer.
 2. Thecurrent transformer assembly of claim 1, wherein the memory chip issituated inside the plug.
 3. The current transformer assembly of claim1, comprising: a third wire between the plug and the memory chip;wherein the memory chip is connected to the second wire.
 4. The currenttransformer assembly of claim 1, comprising: a third wire between theplug and the memory chip; and a fourth wire between the plug and thememory chip.
 5. The current transformer assembly of claim 1, comprising:a second current transformer; and a third wire and a fourth wire betweenthe plug and the second current transformer adapted to transmit ameasurement of the second current transformer; and wherein the memorychip is adapted to store a second scale factor of the second currenttransformer.
 6. The current transformer assembly of claim 5, wherein thememory chip is connected to the second wire and the fourth wire.
 7. Thecurrent transformer assembly of claim 6, wherein the memory chip isadapted to store the first scale factor of the first current transformerand the second scale factor of the second current transformer.
 8. Asystem comprising: a current transformer assembly comprising a plug, afirst current transformer, and a memory chip; a power monitor comprisingat least one processor and at least one memory, wherein the powermonitor is configured to: read a first scale factor for the firstcurrent transformer from the memory chip, receive a first sensor valuefrom the first current transformer, compute a second sensor value fromthe first sensor value using the first scale factor, and use the secondsensor value to determine information about energy consumption in abuilding.
 9. The system of claim 8, wherein the memory chip is situatedinside the plug.
 10. The system of claim 8, wherein the power monitorreads the first scale factor during a startup or initialization process.11. The system of claim 8, the current transformer assembly furthercomprising a first wire and a second wire between the plug and the firstcurrent transformer, wherein the memory chip is connected to at leastone of the first wire and the second wire.
 12. The system of claim 8,the current transformer assembly further comprising a second currenttransformer, wherein the power monitor is further configured to: read asecond scale factor for the second current transformer from the memorychip, receive a third sensor value from the second current transformer,compute a fourth sensor value from the third sensor value using thesecond scale factor, and use the second sensor value and the fourthsensor value to determine information about energy consumption in thebuilding.
 13. The system of claim 12, the current transformer assemblyfurther comprising a first wire and a second wire between the plug andthe first current transformer, a third wire and a fourth wire betweenthe plug and the second current transformer, wherein the memory chip isconnected to at least one of the first wire, second wire, third wire,and fourth wire.
 14. The system of claim 13, wherein the memory chip isconnected to the second wire and the fourth wire.
 15. A method forcalibrating a current transformer, comprising: reading a first scalefactor for a first current transformer from a memory chip in a firstcurrent transformer assembly, receiving a first sensor value from thefirst current transformer, computing a second sensor value from thefirst sensor value using the first scale factor, and using the secondsensor value to determine information about energy consumption in abuilding.
 16. The method of claim 15, wherein reading the first scalefactor is performed during a startup or initialization process.
 17. Themethod of claim 15, wherein the information about energy consumption inthe building includes information about at least a first electricalpower consuming device and a second electrical power consuming device inthe building.
 18. The method of claim 15, further comprising: reading asecond scale factor for a second current transformer from the memorychip, receiving a third sensor value from the second currenttransformer, computing a fourth sensor value from the third sensor valueusing the second scale factor, and using the second sensor value and thefourth sensor value to determine information about energy consumption inthe building.
 19. The method of claim 18, wherein the first scale factoris a first calibration factor for the first current transformer and thesecond scale factor is a second calibration factor for the secondcurrent transformer.
 20. The method of claim 15, further comprisingreading a current transformer identifier from the memory chip.